Yeast

Is yeast an enzyme?

Yeast is not an enzyme. Yeast are living single-celled fungi; enzymes are protein catalysts. In wine, yeast—especially Saccharomyces cerevisiae—produce enzymes that convert grape sugars into ethanol, carbon dioxide, heat, and aroma compounds during alcoholic fermentation.

Winemakers use either native yeasts from grapes and the cellar or selected cultured yeasts for more predictable fermentation. Yeast strain, temperature, nutrient levels, and sugar concentration influence fermentation speed, alcohol tolerance, mouthfeel, and aroma.

After fermentation, dead yeast cells, called lees, can remain in contact with wine during sur lie aging. Lees contact can add texture, savory complexity, and creamy notes, while malolactic fermentation is driven by lactic acid bacteria rather than yeast.